The mitral plastic surgery operation includes a series of procedures suitable to re-establish the correct functionality of the mitral valve, when this is affected by congenital or acquired pathology. Among these procedures, the remodelling of the valve annulus is one of the most frequently used manoeuvres in order to complete and/or to strengthen the valve. Remodelling provides for two moments: the reduction of the annular area and the properly said remodelling, that is suitable to re-establish the normal geometric ratios that are found in natural valves free of pathology. The first one of these manoeuvres is usually carried out with the aid of a prosthesis that is appropriately sutured to the natural annulus. The prosthesis for annuloplastic surgery available on the market are of two types. Flexible annular prostheses, made of various materials, that allow a “linear” reduction of the annular circumference, and rigid and semi-rigid annular prostheses made of various materials, that allow the “linear” reduction of the annular circumference and a geometric remodelling so as to re-establish the physiological systolic shape of the annulus. In the case of semi-rigid prostheses they additionally allow a minimum deformation in order to allow the prosthesis to follow the deformations of the annulus-during the cardiac stages.
All the rigid and semi-rigid annular prostheses have a kidney-like or coupled D shape, with an anterior half-ring, rectilinear in first approximation, that gets sutured in correspondence of the joining of the anterior valve leaflet and a curved posterior half-ring that is sutured in correspondence of the joining of the posterior valve leaflet. The shape of the annular prostheses at issue reproduces the configuration of the valve annulus during the ventricular systole, and therefore in the stage of the valve closing. The ratio between minor axis and major axis is approximately ¾ in all the models currently on the market since it reproduces normal anatomical ratios.
Recently the concept of undersizing of mitral valve annuloplasty has been introduced. This procedure is proposed in case of mitral insufficiency due to a reduced movement of the leaflets as in the case of ischaemic mitral valve or dilated cardiomyopathy. The undersizing consists in using a ring smaller than necessary, though still maintaining the ratio of approximately ¾, and it is carried out in order to bring the base of the anterior leaflet even closer to the posterior leaflet in order to increase the coaptation surface (closure).
The Applicants noticed that in certain pathological conditions, there is a need to modify such ratio in order to make the operation of reconstruction of the mitral valve more effective: for instance in order to bring the valve leaflets closer to each other in the case of anatomical or functional tissue deficiency of one or both leaflets. In addition, it has also been observed that anatomical variation that do not correspond to the ratios reported above are frequent in nature.
In view of the state of the art herein described, a scope of the present invention is to provide an annular prosthesis for mitral valve that can meet the different requirements that have been noticed.